1. Field of the Invention
The present invention relates to a recording medium, and also to a recording apparatus and a reading apparatus compatible with such a recording medium.
2. Description of the Related Art
As a recording medium, a compact disc (CD) is known. Various types of CD-format discs, such as compact disc digital audio (CD-DA), compact disc read only memory (CD-ROM), compact disc recordable (CD-R), compact disc rewritable (CD-RW), and CD-TEXT, all of which belong to the so-called “CD family”, have been developed and are commonly used.
The CD-DA and CD-ROM are read only, while the CD-R is a write-once medium using an organic pigment on a recording layer, and the CD-RW is a rewritable medium using a phase change technique.
On such CD-format discs, data, such as music, video, and computer data, are recorded, and also, track numbers, indexes, and addresses are recorded as sub-codes.
The track number is a number representing a piece of music (track). The indexes are units which form a track, for example, units which partition the movements of a track.
The addresses include absolute addresses represented by consecutive values covering the whole disc and relative addresses represented in units of tracks (which are also referred to as “programs” represented in units of pieces of music). Accordingly, by extracting sub-codes, the absolute address and the relative address at each position of a disc can be identified.
The address is represented by a time value, such as minute/second/frame. Thus, in the CD format, the “time” can be synonymous with the “position (address)”, for example, the “absolute time” corresponds to the “absolute address”.
For example, in the CD format, the sub-code address is represented by minute/second/frame, each having eight bits. Since the eight-bit address is represented in binary coded decimal (BCD), it can express a range from 0 to 99. Accordingly, the “minute” can be designated from 0 to 99 minutes. However, the “second” is inevitably expressed from 0 to 59, and the “frame” is expressed from 0 to 74 since 75 frames, such as frame 0 to frame 74 are defined in the CD format.
On the innermost portion of a disc, sub-code information, such as table-of-content (TOC) information, is recorded. The TOC information indicates an address representing the head and the extent of each track. The content of the address (type of address) can be identified by point information.
For example, if the point information designates a special value, the information described in the corresponding sub-code frame indicates the start address of each track or the first/last track number rather than the absolute address or the relative address.
In recordable discs, such as a CD-R and a CD-RW, a recording track is formed by wobbling grooves. The wobbling waveforms of the grooves are formed by modulating waveforms based on the absolute address information, and thus, the absolute addresses can be identified by the wobbling information of the grooves. Since sub-codes are not yet recorded on a disc without recorded data, the address information is read by the wobbling groove when data is recorded.
In addition to the above-described various types of CD-format (CD-standard) discs, larger capacity discs with high density are being developed, and discs having a plurality of areas whose physical characteristics are different, which are referred to as “hybrid discs”, are also being developed. The variety of the materials and configurations of discs is also being increased.
Under these circumstances, in order to achieve sufficient recording and reading performance of a recording apparatus and a reading apparatus, it becomes necessary to optimize various settings in accordance with the physical characteristics of a loaded disc. For example, the servo gain, laser power, and access range should be optimized.
It is, however, difficult to sufficiently determine the physical characteristics of the individual discs loaded in a recording apparatus or a reading apparatus. Certain calibration may be performed when a disc is loaded, and even so, it is still difficult to precisely determine the physical characteristics of the loaded disc. Additionally, since the burden is increased by the calibration operation, the amount of software and hardware must be increased, and also, it takes a longer time before a recording or reading operation is started.
Accordingly, there is still a demand for easy and precise determination of the physical characteristics of discs without impairing the compatibility with known CD-format discs or increasing the complexity of hardware and software used in a recording apparatus and a reading apparatus.